Changing Air Filter

[chur2936]

Dose anyone know if changing the GZ250's air filter with a higher performance one will help increase top end and also not effect how the bike sounds and handles?

Thank you, Christian

2008 GZ250
2,853 Miles (so far)

[grasshopper]

welcome to the forum. I have not tried any air filter mods on my gz250 yet. I did do some on my gs500e. the k&n filter replacement worked fine without having to rejet the carbs. then I removed the factory air box and added pod filters and it dropped my top end and was sluggish between 1/4 throttle and 3/4 throttle. rejetting the carbs needed to be done to fix the problem. other people on this forum have posted good info on this subject. you might wanna read those. try the search engine to navigate through them faster. I hope I was able to help.

[JWR]

What is the top sped now?
Road, weight of rider, and weather conditions have more to do with top speed than and mods that you can do.

Most air and exhaust mods create more problems than make gains.
75 to 80 mph speeds are what most GZ's will do stock.

[Water Warrior 2]

I agree. 80 is good, anything over 80 is a bonus but the GZ will not like that speed for long. A maximum cruising speed in good conditions seems to be 60 to 65 to keep the bike happy.
Trying to mod a GZ is not a great return for the time and money that can be invested. Ride the bike according to it's capabilities and accept them. If you need more speed and power then you need more bike under your butt. There are lots of slightly larger and just larger bikes to fill the requirements.

[Cathy]

Qasual - The HWY in Vancouver is 80km/h and I usually do 55-60mph (88km/h-96km/h), the GZ is very happy with those speeds and not too much in the vibration department as well. As everyone else said, if you want more speed and power. You're looking at more of a bike.

[blaine]

You won't gain much in performance but you can save about 50% by using the Hiflo-Filtro Hfa-3503 air filter.It is a direct bolt in & will breath better than the OEM.Because it is more of a open design it will make the intake a little louder. :) ;)

[raul10141964]

yes, but you may need to change the main jet to compensate for the extra air.
I'm running:
mod air filter
140 main
2.5 turns on the pilot
and 16T sprocket
I am very happy with the results

[kori]

yes, but you may need to change the main jet to compensate for the extra air.
I'm running:
mod air filter
140 main
2.5 turns on the pilot
and 16T sprocket
I am very happy with the results


ive done nearly this same mod.
EMGO Cone Air Filter attached directly to carb intake
(no air box)
135 main jet
2.5 turns out on the pilot jet
15T front sprocket
(havent changed due to the 50/50 view on this forum)

should i also shim the needle?
acceleration from dead stop is great, i just feel that that it could have more.

[raul10141964]

I try to upload
Adjusting the Carburetor.pdf
Mikuni Carb Theory.pdf
but the file limit of the forum is to low

[blaine]

ive done nearly this same mod.
EMGO Cone Air Filter attached directly to carb intake
(no air box)
135 main jet
2.5 turns out on the pilot jet
15T front sprocket
(havent changed due to the 50/50 view on this forum)

should i also shim the needle?
acceleration from dead stop is great, i just feel that that it could have more.
You should shim the needle.I bet your running lean in the mid-range. ;) :)

[kori]

You should shim the needle.I bet your running lean in the mid-range. ;) :)

so shim.
got it.

question- how much?

also ever read that moving the existing washer is a way of doing it but i imagine that doesnt raise the needle like i need.

[blaine]

so shim.
got it.

question- how much?

also ever read that moving the existing washer is a way of doing it but i imagine that doesnt raise the needle like i need.
Yes it does.When you follow the instructions & see it when you take it apart.It will become clear.
http://www.gz250bike.com/forum/showthread.php?t=16

;) :) :)

[kori]

thats the post im talking about.
:D

blaine after the needle adjustment, that's letting in more air to the mixture, correct?

if that is so, will i have to re-adjust the pilot? say screw it in all the way and back it out maybe half(1.25) of what i have at the moment(2.5)

thank you in advanced for the rapid replies. ive had this gz for awhile and stumbled upon this website lately. its revived my interest in the little thing. before it just sat in my backyard under a tarp. :o:o

[blaine]

thats the post im talking about.
:D

blaine after the needle adjustment, that's letting in more air to the mixture, correct?

if that is so, will i have to re-adjust the pilot? say screw it in all the way and back it out maybe half(1.25) of what i have at the moment(2.5)

thank you in advanced for the rapid replies. ive had this gz for awhile and stumbled upon this website lately. its revived my interest in the little thing. before it just sat in my backyard under a tarp. :o:o
Raising the needle lets in more fuel.The needle controls mid-range,the pilot controls idle to 1/4 throttle.You need to adjust pilot also.You need to adjust it with the bike running warmed up.Adjust to were the bike idles fastest & smoothest.Your at 2.5.Turn out (rich) slowly you will hear the bike speed up.When the bike starts to stumble back in till idle is smooth.
;) :)

[kori]

pilot jet is inside the float bowl of the carb.
this is what you are referring to right?

the air/fuel mixture is the one on the outside of the bowl that i drilled the cap out of. is this the one you mean? not quite sure how i would adjust the pilot while running.

[blaine]

pilot jet is inside the float bowl of the carb.
this is what you are referring to right?

the air/fuel mixture is the one on the outside of the bowl that i drilled the cap out of. is this the one you mean? not quite sure how i would adjust the pilot while running.
Pilot jet & air/fuel mixture are the same thing.(the one you drilled the cap off) ;) :)

[kori]

oh ok.

i will try the new adjustments after work tomorrow hopefully. its supposed to be freezing here so i dont really no how great the tune will be. hopefully with the needle mod i get this old thing running a little more pep in its step.

[blaine]

oh ok.

i will try the new adjustments after work tomorrow hopefully. its supposed to be freezing here so i dont really no how great the tune will be. hopefully with the needle mod i get this old thing running a little more pep in its step.
With the pilot jet (idle mixture) adjusted (richer),you will find that the bike will start easier cold.Less choke needed. ;) :)

[alantf]

North America must be the only country in the world that legislates for vehicles that won't run at their best , from the factory. Every other country lets the manufacturers set up the vehicles for maximum efficiency. I've never had to touch the carb on my European GZ. :mad:

[blaine]

North America must be the only country in the world that legislates for vehicles that won't run at their best , from the factory. Every other country lets the manufacturers set up the vehicles for maximum efficiency. I've never had to touch the carb on my European GZ. :mad:

Yep.....Set to the point that they are so lean that they will not start well in the cold. ;) :)

[Water Warrior 2]

Experience over the years is wonderful to fall back on. I love a modern FI engine because they run so well. There is one exception though. COLD WEATHER. AN old carb engine will start better at real cold temps and run more economically. FI engine will run richer in the winter to compensate for the temps. Nor will they run at the proper operating temp sometimes. I had a 1996 Ranger 4 cylinder that was terrible in the winter. Easy fix. Took the fan off the front of the engine. No fan blast on the engine and sensors let the engine warm up and run the same MPG as summer. The engine fan noise was not there as an added benefit. If I still lived in the prairies my slug 4.0 Ranger would get the same treatment.